Since their introduction in 1997, “smartphones” have gained rapid market acceptance. Smartphones provide the user with advanced features in addition to being able to make voice calls. For example, smartphones typically have internet connectivity, high resolution cameras and touch-screen displays, and powerful CPUs. The rapid acceptance of smartphones has been driven by a combination of falling prices and increasingly sophisticated features. In addition, there is a growing ecosystem of applications that take advantage of smartphones' sensors, displays, and ability to connect to powerful computing and data storage capabilities that are available in the “cloud.” The built-in capabilities of smartphones can be further extended through the addition of accessories that enable the phone to sense different types of information. For example, it is already possible to find commercial lens systems that enable the phone to be used as a rudimentary microscope with a 350× magnification, which is sufficient for capturing images of cells, bacteria, and biological tissue. Breslauer et al., Plos One, vol. 4, Jul. 22, 2009 and Smith et al., Plos One, vol. 6, Mar. 2, 2011. Smith et al. also demonstrated that, with addition of a light collimation system and a diffraction grating in front of the camera, a smartphone may function as a spectrometer with a wavelength resolution of 5 nm. The ability of a smartphone camera to take images of the colored label components of a biological assay have been applied to lateral flow immunoassays (Mudanyali et al., Lab Chip, vol. 12, pp. 2678-86, 2012), quantum-dot labeling of bacteria (Zhu et al., Analyst, vol. 137, pp. 2541-2544, 2012), and fluorescence microscopy (Breslauer et al.). Further, smartphone cameras have recently been exploited for microfluidic and optofluidic applications (Martinez et al, Analytical Chemistry, vol. 80, pp. 3699-3707, May 15 2008 and Zhu et al., Analytical Chemistry, vol. 83, pp. 6641-6647, Sep. 1, 2011) and as a lens-free microscopy tool (Tseng et al., Lab on a Chip, vol. 10, pp. 1787-1792, 2010).
Such approaches, however, have not involved biomolecular assays with label-free detection. Detection of an analyte through one of its intrinsic physical properties (e.g., dielectric permittivity, mass, conductivity, or Raman scattering spectrum), called “label-free” detection, can be preferable for assay simplicity in terms of the number of reagents required, washing steps needed, and assay time. Of all the label-free detection approaches that have been demonstrated, those based upon optical phenomena have been most commercially accepted due to a combination of sensitivity, sensor cost, detection system robustness, and high throughput. Adsorption of biomolecules, viral particles, bacteria, or cells on the surface of an optical biosensor transducer results in a shift in the conditions of optimal optical coupling, which can be measured by illuminating the transducer surface, and subsequently measuring a property of the reflected or transmitted light. Such a detection approach is extremely robust, and has become economically advantageous due to the advent of low cost light emitting diodes (LEDs), semiconductor lasers, and miniature spectrometers. For example, surface plasmon resonance (SPR) based biosensors and photonic crystal (PC) optical biosensors are capable of detecting broad classes of biological analytes through their intrinsic dielectric permittivity. Each approach has been implemented in the form of large laboratory instruments and miniaturized (shoebox-sized) systems. However, no prior label-free optical biosensor instrument has been fully integrated with a smartphone, using the camera in the phone itself as the detection instrument.